The elevator cars in such multi-mobile elevator installations are typically each equipped with an associated drive and an associated braking system. The electronic control of the entire elevator installation is frequently designed so that no collisions of the individual elevator cars should happen. Particularly in the case of an emergency stop or even in the case of a normal floor stop of a car, it cannot be ensured in all circumstances that a further elevator car disposed above or below in the same elevator shaft can still stop in good time in order to avoid a collision. This could be avoided by presetting, via the control, sufficient spacings between the individual elevator cars and also appropriately adapted vertical speeds. However, the conveying capacity of a multi-mobile elevator installation is not fully utilized due to such a preset, which has an influence on the cost/utilization efficiency.
A multi-mobile elevator installation is known from European Patent Specification EP 765 469 B1, which comprises means for opening the safety circuit of an elevator car if an undesired approach to another elevator car occurs. According to the stated patent specification there are present, at each elevator car, safety modules which evaluate the car positions and speeds so as to be able to trigger, in a given case, braking processes even at other elevator cars. The individual safety modules have to constantly know and evaluate the car positions and speeds of the other participating elevator cars in order to be able to correctly react to an emergency situation. A special decision module is needed for that purpose, which is responsible for determination of the stop commands in the emergency case.
A similarly complicated solution is known from International Patent Application WO 2004/043841 A1.